An plane sprays coca plants in El Catatumbo, Norte de Santander department. Colombia is the only coca-producing country to allow aerial spraying.
Photograph: AFP/Getty Images

For more than two decades crop dusters have buzzed the skies of Colombia showering bright green fields of coca with chemical defoliant as part of a US-funded effort to stem the country’s production of cocaine.

Colombian farmers count cost of assault

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Farmers across the country have long complained that indiscriminate spraying also destroys legal crops, and that the chemical used – glyphosate – has caused everything from skin rashes and respiratory problems to diarrhoea and miscarriages.

Authorities in Colombia and the United States – which has funded the aerial eradication programme with as much as $2bn since 2000 – scoffed at those claims, and argued that aerial spraying was the most effective and safest method of destroying coca plants – the raw material for cocaine.

But after 20 years and 4m acres sprayed, Colombia now appears poised to make a dramatic about-face on what was once the keystone of its US-backed drug-fighting strategy.

A decision on the recommendation is expected to be made at a meeting on 14 May of the National Narcotics Council, the body which sets Colombia’s drug policy.

“It would be unacceptable, even from an ethical standpoint, to have this evidence on the table and not accept it,” said the health minister, Alejandro Gaviria, a member of the council.

The United States, which made the spraying programme an axis of its counter drug policy in Colombia, has staunchly defended use of the chemical, which is marketed by Monsanto under the name RoundUp.

“Colombia is a sovereign country and it must do what reflects its national interest, but they should take a serious look at the scientific evidence,” said William Brownfield, US assistant secretary of state for counter-narcotics, and a former ambassador to Colombia.

“There is not one single example of a person who has suffered damages from glyphosate in Colombia in the past 20 or 21 years,” Brownfield told Caracol Radio.

A farmer harvests coca leaves in a plantation in the mountains of the department of Cauca, Colombia. Photograph: Luis Robayo/AFP/Getty Images

The looming possibility of an end to defoliant spraying in Colombia appears to have prompted the White House to bring forward publication of its annual report on coca cultivation in the country. The figures released on Monday showed a sharp spike in coca cultivation last year after six straight years of steady or dropping production. The land under coca cultivation in 2014 was up 39% to 112,000 hectares, according to the Office of National Drug Control Policy. Potential cocaine production jumped 32% to 245 tonnes.

One State Department official suggested that the 2014 coca numbers would convince Colombian officials that cutting the spraying programme would be a mistake, despite the health concerns.

Under pressure from the United States, Colombia began allowing the large-scale coca spraying programme in 1994. To date Colombia has sprayed more than 4m acres, an area slightly larger than the US state of Connecticut.

It is the only country where coca is grown that allows aerial spraying, in part because its half-century-old internal conflict with leftist rebels prevents on-the-ground access to many remote areas of the country where coca is cultivated and protected by insurgents. Peru and Bolivia, also coca producers, fight the illegal crops through manual eradication.

But the justice minister, Yesid Reyes, who met the White House drug czar, Michael Botticelli, in Washington on Monday, told reporters that the Colombian government could not endanger its citizens. “If a programme like the eradication of illegal crops through aerial aspersion has the possibility of harming the health of Colombians, the state has the obligation to protect its citizens,” said Reyes, who holds a seat on the narcotics council.

Other council members disagree: the government inspector general, Alejandro Ordóñez, warned that ending the spray programme would play into the hands of leftwing Farc rebels who reap huge profits from the drug trade.

The Farc began peace negotiations with the government of President Juan Manuel Santos in 2012 in Havana. One of the three points already agreed is fighting drugs. In the draft agreement the guerrillas commit to helping eradicate coca and the government vows to use aerial spraying only as a last resort, favouring voluntary eradication by peasants themselves.

The agreement will only enter into force if and when a peace deal is reached, but Farc negotiators last week called for an immediate application of the accord.

Former president Alvaro Uribe, now an opposition senator, said that if for health reasons glyphosate cannot be used, a substitute should be found but that the government should not suspend the programme “to please the Farc”.

But even if glyphosate were safe, or a safer alternative is found, continuing to use aerial spraying as a strategy against illegal crops is a bad idea, argued Adam Isacson, an analyst of US drug policy in Colombia.

Colombian miners search for gold near a mine that collapsed in the department of Cauca. Photograph: Luis Robayo/AFP/Getty Images

He noted that the spike in production last year occurred while the aerial eradication programme remained in place, and was due to low eradication efforts overall, in part because of a suspension of spraying for several months after three planes were shot down. “Last year saw the lowest amount of total eradication since the 1990s,” he said.

Lower gold prices may also have been a factor. When gold prices began to surge in 2009, many coca farmers found it more lucrative to find new work in unregulated gold mines. “Illegal gold mining worked well as an alternative to coca,” says Isacson. When gold prices started to drop in 2013, coca once more became a more attractive prospect again.

The largest reductions in coca cultivation occurred when the Colombian government shifted its focus to manual, on-the-ground eradiation starting in 2007, sending out teams to yank the bushes from the ground.

At the time, Santos, who was then defence minister, said “Manual eradication can be more effective and at times, cheaper’’ than aerial spraying.